Delay blasting cap



Dec. 21, 1937. M. PALMIERI ET AL DELAY BLASTING CAP Filed March 9, 1936 and o Ru 11w 'PEY 5 INVENTOR JAMUEL 0 [mu/cw MA I?! ATT Patented Dec. '21, 1937 PATENT OFFICE DELAY BLASTING CAP Mario Palmieri, South Glastonbury, and Samuel D. Ehrlich, Glastonbury, Conn.

Application March 9, 1936, Serial No. 67,926 9 Claims. (Cl. 102-10) This invention relates to blasting caps and particularly to a means employed in the cap to control the length of time between applying the electric current to the cap and the detonating or I igniting of the explosive charge.

A primary object of the invention is to provide an improved delay blasting cap enabling the delay to be more accurately controlled-and varied over a wide range by predetermined difierences of timing. 4

Another object of the invention is to provide a heating compound ignited preferably by an igniting compound in contact with the electric wires and which will heat a metallic member 1 within or surrounding the heating compound so that the igniting compound will set off the main charge only after the metallic member has been sufiiciently heated to ignite the detonating compound.

-A feature that enables us to accomplish the above named objects is that the heating compound may becontained within a unit including an amount of inert material so that by varying the proportions or amounts of heating compound and inert material, the time taken for the metallic element to become sufliciently heated to ignite the detonating material may be Widely varied and accurately controlled.

With the above and other objects in view our invention may include the features of construction and operation set forth in the following specification and illustrated in the accompanying drawing.

In the accompanying drawingannexed hereto .and forming a part of this specification, we have shown our invention embodied in two difierent forms of delay blasting caps but it will be understood that the invention can be otherwise embodied and that the drawing is not to be construed' as defining or limiting the scope of the invention, the claims appended to this specification being relied upon for that purpose.

In the drawing:

5 Fig. 1 is a central longitudinal section of a complete blasting cap provided with the present invention.

Fig. 2 is a view similar to Fig. 1 but showing a different form of the invention.

50 Fig. 3 is a view similar to Figs. 1 and 2 showing a difierent packing of the igniting means within the unit, and

' Fig. 4 is a horizontal section taken on the plane of line l4 of Fig. 3.

55 I In the above mentioned drawing, we have shown several embodiments of the invention which are now deemed preferable, but it is to be understood that changes and modifications may be made within the scope of the appended claims without departing from the spirit of the 5 invention.

Briefiy 'and in its preferred aspect, our invention may include the following principal parts: first, a blasting cap having a detonating mixture such as fulminate. of mercury within one end, 10 the amount being sufficlent to set ofi a principal charge of explosive; second, a heating mixture or compound within a unit and associated with an amount of inert material; third, a metallic element intimately associated with the heating mixture and in contact with the detonating mixture so that the latter mixture may be heated by conduction of heat through the metallic element from the heating mixture to a sufiicient degree to ignite the detonating mixture or com- 20 pound; fourth, -an igniting compound closely associated with the heating compound; fifth, firing means for the igniting compound such as a resistance wire through which a current of electricity may be applied, and sixth, enclosing and sealing means for the entire blasting cap.

Referring more in detail to the figures of the drawing and first to Fig. 1, we provide a simple casing I0 within which all parts of the blasting cap may be enclosed. This casing Ill may be in the form of a thin metal .tube closed at one end. Within the part of the tube adjacent the closed end is placed a quantity of detonating mixture II. This mixture Il may be ofany desired material such as fulminate of mercury or other detonator of any type. The amount of detonating mixture may be varied for different services for which the blasting cap may be designed and should be suflicient to detonate the charge of explosive of any type that may be used with the cap.

Adjacent the detonating compound or mixture l l and preferably lying directly against its upper surface is a .casing l2 the one shown in Fig. 1

that portion adjacent the mixture II is a quantity of inert material such as sand or other inactive material I4. Above the inert material I4 and extending preferably to the upper end of the casing I2 is a quantity of non-explosive nongaseous heating compound I5. The amount of this compound I5 is sufiicient when ignited and burned to heat the metallic casing I2. When thus heated the end in contact with the detonating mixture will be heated by conduction along the casing I2 sufliciently to set ofi this mixture. By varying the amount of heating mixture I5 within the casing ,I2 the time taken to heat the.lower end of the casing I2 may be widely varied. By varying the ingredients of the mixture I5, the quantity of mixture and the heat conducting qualities of the casing I2 the time taken to sufficiently heat the casing I2 at its lower end to detonate the fulminate or other detonating mixture II may be widely varied. As the mixture I5 is substantially non-gas producing there is no material increase in pressure created within the cap to explode or burst the casing Ill prior to detonating the mixture II. Also, there is insufficient heat transmitted through the casing I2 to ignite such explosives as black powder or dynamite prematurely, that is, prior to detonating them.

To ignite the heating mixture I5 there may be provided a small quantity 'of a suitable igniting compound I6, preferably directly in contact with the upper surface of the heating mixture I5. This igniting material may be of any suitable composition sufiiciently sensitive for this purpose. The igniting compound I6 may be fired by the heat of a resistance wire IT in circuit with the cap wires I 8 in the usual manner.

Above the igniting mixture I6 there may be provided within the upper part of casing I0 sealing elements I9, 20 and H, such as compositions of asphaltum rubber and/or sulphur to exclude moisture and to retain the materials of the cap in fixed position. These substances also closely surround the cap wires I8 and form insulation therefor.

Preferably the casing I2 is continued above the heating mixture I5 and igniting mixture I6 to form a self-contained unit that may be separately manufactured and inserted in the cap in a single operation rather than being built up for each cap as it is made. This unit may contain in addition to the materials I4, I5 and IIireferred to above an insulating member 23 resting upon the igniting material I6 and the sealing composition I9. All of these elements of the unit may be assembled within casing I2 and the insulating enclosure I3 may be placed around the unit independently of the particular cap and detonating material with which it is to be used. Each unit would be made up for a particular delay and units having particular periods of delay may be assembled in large numbers. In making up complete caps units having difierent delays may be applied to caps having difi'erent types and amounts of detonating mixtures II for diflerent services.

In Fig. 2 there is shown a modified form of the unit including the heating and igniting materials I5 and I6. The casing I 0 and the detonating material I I may be similar to those described above in connection with the form of the invention shown in Fig. 1. The unit casing 25 as shown in Fig. 2 for the unit containing the heating mixture 26 is formed of heat insulating material such as asbestos or other mineral fibre and preferably of a non-gasifying substance.

Within this casing 25 is placed an amount of inert material 2'! directly below the heating mixture 25 as in Fig. 1. Extending centrally through the lower part of the unit formed within the casing 25 is a metallic heat conducting rod or bar 28. This rod is imbedded in the heating mixture 26 and passes through the inert material 21 and also through the bottom enclosing wall of the casing 25. The rod 28 is therefore in direct contact with the detonating mixture II at one end.

The unit formed within casing 25 also has a small amount of igniting mixture 29 directly above and in contact with the heating mixture 26. The upper end of the unit above the igniting material 29 has an insulating layer 30 and a substantial thickness of sealing material 3| through which the cap wires 32 extend. The open upper end of the casing 25 may be crimped over as shown to aid in retaining the materials within the unit. This unit, similarly to the unit referred to above, may be made up separately from the caps and added to the cap as a complete unit during the assembling of the. cap materials.

Fig. 3 shows a cap generally similar to that illustrated in Fig. 1 but having different relative amounts of inert material I4 and heating mixture I 5. Above the igniting. material is placed a disk 33 of hard material and through which extends a transverse elongated slot 34. Through this slot 34 may pass the cap wires 35 to the igniting material I6.

As the heating materials I5 and 26 and the igniting materials I6 and 29 are or may be preferably substantially non-gasifying, the outer casing I0 is not required to be vented. If, however, venting of the casing is desired there may be provided a few holes 36 as shown in Fig. 1 adjacent the igniting material I 6 and above the metal casing I2 for the heating material I-5.

We claim as our invention:

1. A delay blasting cap comprising in combination, a casing, a detonating mixture therein. a heating mixture spaced from said detonating mixture, a heat conducting metal in heating proximity with said heating mixture and in contact with said detonating mixture and igniting means for said heating mixture in contact therewith.

2. A delay blasting cap comprising in combination, a casing, a detonating mixture therein, a heating mixture spaced from said detonating mixture, an amount of inert material disposed between said heating and detonating mixtures, a heat conducting metal in heating proximity with said heating mixture and in contact with said detonating mixture, and igniting means for said heating mixture.

3. A delay blasting cap comprising in combination, a casing, a detonating mixture therein, a

4. In a delay blasting cap, an igniting fg comprising in combination, a small metallic casing adapted to fit within the cap and closed at arcades 3 one end, inert material within said casing adja-v cent the closed end, a heating mixture adjacent the opposite end of said casing and an igniting mixture in contact with said heating mixture.

5. In a delay blasting' cap, an igniting unit comprising in combinatioma casing adapted to fit within the cap, a heating mixture at one end and an inert material at the opposite end, heat conducting means extending from one end to the other of said casing, and igniting means for said heating mixture within the casing and adjacent the heating mixture.

6. In a delay blasting cap, an igniting unit comprising in combination, a small metallic heat conducting casing adapted to fit within the cap and closed at one end, inert material within said casing and adjacent the closed end thereof, a heating mixture within said casing remote from said closed end, and igniting means for said heating mixture.

7. A delay blasting cap comprising in combination, a casing, a detonating mixture therein, an

igniting unit within said casing having a heat conducting element in contact with said detonating mixture, a heating mixture within said unit spaced from said detonating mixture and in contact with said heat conducting element, and means in contact with said heating mixture to ignite said heating mixture.

8. A delay blasting can comprising in combination, a casing, a detonating mixture therein, an igniting unit within said casing having a heat conducting element in contact with said detonating mixture, a heating mixture within said unit spaced from said detonating mixture and in contact with said heat conducting element, means in contact with said heating mixture to ignite said heating mixture, and means to enclose said unit within said cap.

9. A delay blasting cap comprising in combination, a casing, a detonating mixture therein, an igniting unit within said casing having a heat conducting element in contact with said detonating mixture, a heating mixture within said unit spaced from said detonating mixture and in contact with the heat conducting'element, heatinsulating means between the unit and the cap, and means to ignite said heating mixture.

' MARIO PAL-MIERI.

snmm. D. EHRLICH. 

